Spray gun with self-purging nozzle



L. c. RENNIE April 2, 1968 SPRAY GUN WITH SELF-PURGING NOZZLE Filed March 21, 1966 FIG. 2

A-w REM c; 600 0616 ?ENN1 United States Patent 3,375,978 SPRAY GUN WITH SELF-PURGING NOZZLE Lawrence C. Rennie, Johannesburg, Transvaal, Republic of South Africa, assignor to Rand Mines Limited, Johannesburg, Transvaal, Republic of South Africa Filed Mar. 21, 1966, Ser. No. 535,997 3 Claims. (Cl. 239113) ABSTRACT OF THE DISCLOSURE The body of the spray gun has two concentric liquid discharge nozzles and a concentric air discharge nozzle. There is a manually operated valve assembly in the body having two terminal positions. The body further has independent liquid and air feed passages extending between each inlet and corresponding nozzle. The valve assembly, in one terminal position, connects the liquid inlets to the corresponding discharge nozzle through the independent liquid and air feed passages, and in the other terminal position closes both liquid inlets and automatically con nects the air inlet to both liquid feed passages and air feed passage. The body further has a separate and independent manually controlled air inlet valve which maintains the air inlet open throughout the spraying operation.

This invention relates to spraying apparatus and more particularly to spray guns which will eifect mixture of two liquids on emission from the apparatus.

,It is frequently desirable that certain liquids such as.

synthetic resins, latex and other emulsions be sprayed onto surfaces together with suitable coagulating or curing or gelling agents to ensure the adequate coagulation or curing of the emulsion or liquid with a minimum delay. Spray guns have been designed for carrying out such operations and particularly for use when it is impractical to mix the liquid or emulsion being sprayed with the catalyst or coagulating agent prior to the spraying operation. Since any mixing of the resin or latex with the catalyst or coagulating agent inside the gun will normally result in clogging, guns have ben designed in which these two components emerge as separate sprays from the gun and only become admixed outside the gun. In spite of this clogging does still occur after a spraying operation when the gun is laid down, this being due to residual amounts of one liquid component in the gun flowing around the exit nozzle to contact the other component. The result of this is that the gun must be dismantled and cleaned which is onerous and time wasting during the course of spraying operations.

It is one object of this invention to provide a gun designed to prevent such clogging occurring.

A further object is to provide a spray gun which is small and light so that it is easily held, which produces an eifective spray and which is easily dismantled for cleaning at the end of a days spraying operations.

In accordance with this invention there is provided a spray gun comprising a body incorporating a pair of concentric liquid discharge nozzles and a further air discharge nozzle, a manually operated valve assembly in the body, liquid and air inlet connections on the body, and independent liquid and air feed passages in the body extending between each inlet and corresponding nozzle, the said valve assembly in the one terminal position connecting the liquid inlets to the corresponding discharge nozzles through the independent feed passages, and in the other terminal position closing the liquid inlets and connecting the air inlet to at least one liquid feed passage.

Other features of the invention will be apparent from the following description in which reference is made to the attached drawings in which:

FIG. 1 is a plan of the spray gun with the top cover removed; and

FIG. 2 is a section on the line A-A in FIG. 1.

As shown in the drawings, the spray gun comprises a body I mounted on a handle 2. The rear portion of the body 1 has laterally spaced cylindrical apertures 3 bored therethrough in which sleeves 4 are fitted. Fitted in each sleeve 4 is a spool valve 5 having a bottom extension 6 connected adjacent the cranked portion of a bell crank lever 7. The one arm 8 of the lever 7 is pivotally attached to an extension 9 of the body by a pin 10, and the other arm 11 extends adjacent the handle 2. With the arm 11 pulled adjacent the handle 2 as shown in FIG. 2 the spool valves 5 will be in the raised position illustrated where they allow a connection between liquid inlet connections 12, 13 on the body 1 and corresponding liquid feed passageways 14, 15 in the body.

When the arm 11 which is loaded by a spring 16 is released the spool valves 5 move to the lower terminal position where they disconnect the liquid inlets 12, 13 from the corresponding feed passages 14, 15 but connect the latter to the area above the spool valves 5. Although the spool valves 5 have been shown with one top sealing ring, two sealing rings one above the other are normally necessary.

This area above both the spool valves is connected to the air inlet connectionby the transverse passageway 17 which in turn is connected to an air feed passage 18 in the body. The spaces above the spool valves are closed by a cap 19 provided with spigots 20 fitted with ring seals 21 and the pressure of air in said spaces acts to press the valve 5 downwardly and assists the action of spring 16.

The air flows from the passage 18 through the outer of three concentric nozzles 22, 23, 24, in the front of the body 1. The innermost nozzle 24 is connected to the passage 14 and the intermediate nozzle 23 to the passage 15.

Thus when the spool valves 5 are in the raised position liquid may flow from inlet 13 past the corresponding spool valve 5, through feed passage 14 and be discharged through nozzle 24. At the same time liquid may fiow from inlet 12 past the corresponding spool valve 5 through passage 15 and be discharged through nozzle 23.

With the spool valves 5 in the raised or lowered position air may flow from air inlet 25 through feed passage 18 to the air discharge nozzle 22. However, with the spool valves 5 in the lowered position the liquid feed passages are disconnected from the corresponding inlets 12, 13 and connected to the air inlet 25. Thus every time the arm 11 is released to stop a spraying operation, the air flow is automatically diverted through the liquid feed passages 14, 15 and nozzles 23, 24, and acts to clean the liquid therefrom. Accordingly, if the gun is laid down after a spraying operation there is negligible danger of the one liquid discharge nozzle becoming clogged through a flow of liquid into it from the other liquid discharge nozzle. It will be appreciated that the liquid feed passages in the gun are wholly independent and sealed from each other so that no mixing of the two liquids can occur in the gun during a spraying operation.

Essentially it should only be necessary to use the air flow to clean out one liquid passage and nozzle, but it is preferred to use this flow to clean out both passages and nozzles since even very small amounts of certain catalysts or coagulants can cause curing or coagulation of certain resins or latex. Also a certain amount of clogging may occur due to lumps or foreign matter in the liquid supplies. With the arrangement described these can often be cleared by moving the lever a few times to discharge air through the liquid passageways.

The gun illustrated has been specifically designed for spraying latex and a calcium chloride solution coagulant. The calcium chloride solution supply is connected to the inlet 12 which is fitted with a needle valve 26 for accurate metering of the coagulant in relation to the latex fiow. The latex supply is connected to inlet 13 and the air supply to inlet 25 which is fitted with a valve 27 to close off the air supply when spraying operations are stopped for any appreciable period. The valve 27 also allows for a degree of control of the rate of air supply. All fluids are fed to the gun under pressure.

In spite of the measures taken for prevention of clogging, persistent clogging can still occur due mainly to inefl-icient filtering of the liquids fed to the gun. For this reason the spray nozzle assembly is made easily removable for cleaning purposes. Thus the centre spray nozzle 24 is formed by the bore of a tubular member 28 fitted with a ring seal and which is a sliding fit in socket 29. The flange 30 on member 28 limits its penetration into socket 29.

The intermediate spray nozzle is formed by the annulus between member 28 and a sleeve 31 fitting over it. The latter is fitted with a ring seal, is a sliding fit in socket 32, and is located against flange 30' and a shoulder 33 on the centrally bored cap 34. The cap 34 is screwed onto the outer end of the body, finger tight, and the outer nozzle 22 is formed by the annulus between the bore of the cap 34 and the external surface of sleeve 31.

It will be noted that the outlet nozzles decrease in diameter considerably towards the exit ends. This is done to cause a free vortex swirl to take place and ensure intimate mixing of the two liquid components outside the gun. Since the degree of such mixing will vary it the direction of the one swirl varies in relation to the other, the tubular member 28 and sleeve 31 are both fitted with helical guides 35 and 36 to ensure that the swirls from both nozzles 22, 23, occur in the same or predetermined directions.

While the gun has been illustrated as embodying a concentric annular air nozzle 22, the shape of this nozzle may be varied to shape the emergent spray to suit specific applications in a manner known in the art.

What I claim as new and desire to secure by Letters Patent is:

1. A spray gun comprising a body incorporating t'wo concentric liquid discharge nozzles and a further concentric air discharge nozzle, a manually operated valve assembly means in the body, liquid and air inlet connections on the body, and independent liquid and air feed passages in the body extending between each inlet and corresponding nozzle, the said valve assembly means in the one terminal position connecting the liquid inlets to the corresponding discharge nozzles through the independent liquid and air feed passages, and in the other terminal position closing both the liquid inlets and automatically connecting the air inlet to both liquid feed passages and the air feed passage, and a separately and independently controlled air inlet valve maintaining said air inlet open throughout the spraying operation.

2. A spray gun as claimed in claim 1 in which the body is mounted on a handle and the valve mechanism comprises two spool valves operable by movement of a lever mounted adjacent the handle.

3. A spray gun as claimed in claim 1 in which the liquid discharge nozzles are formed by a tubular member and a sleeve fitting over but spaced from the tubular member both the tubular member and sleeve being a sliding fit in sockets in the body, and said sleeve being retained in.

position by a centrally bored cap screwed onto the body the cap bearing against a projection on the sleeve, and the bore of the cap being spaced from the sleeve to define an annular air outlet nozzle.

References Cited UNITED STATES PATENTS 1,233,423 7/1917 Wallace 239--415 2,511,719 6/1950 Kirkham 239-415 X 2,761,737 9/1956 Nurkiewicz 239-424.5 X 2,887,736 5/1959 Barrett 239113 X 3,232,540 2/1966 Cassanmagnago 239-424 X FOREIGN PATENTS 1,180,199 10/1964 Germany.

M. HENSON WOOD, JR., Primary Examiner.

H. NATTER, Assistant Examiner. 

